Methods for evaluating the rebound resilience of polymer materials are defined in JIS K6255 “Rubber, vulcanized or thermoplastic—Determination of rebound resilience”. Generally used is a lupke-type rebound resilience test where a pendulum is used to calculate values of rebound resilience from the height from which the pendulum is dropped and the height to which the pendulum rebounds (see Non-Patent Literature 1).
In the case of using a lupke-type rebound resilience tester, the lower the energy loss during the swinging movement of the pendulum, the higher the experimental accuracy. JIS K6255 defines testing methods for determining the period of free oscillation of the pendulum and the logarithmic decrement as a measure of accuracy of measured values.
However, such physical evaluation methods, as by dropping a pendulum made of metal or the like onto a polymer material, give very large errors, failing to provide satisfactory measurement accuracy. Another problem is that, in cases where the difference in value between samples is small, the difference cannot be evaluated with good reproducibility. In addition, the methods include no method for evaluating the molecular structure in detail.
Meanwhile, for polymer materials such as rubber materials, the hardness is an important physical quantity that affects various properties of products. For example, the hardness of tires, which are rubber products, is closely linked to the properties including handling stability and the performance on ice and snow. Widely known methods for measuring the hardness of rubber products are in conformity with JIS K6253 (see Non-Patent Literature 2).
However, the measurement methods using a JIS hardness tester give large errors, failing to provide satisfactory measurement accuracy. Another problem is that, in cases where the difference in value between samples is small, the difference cannot be evaluated with good reproducibility.
Furthermore, for polymer materials such as rubber materials, the energy loss is also an important physical quantity that affects various properties of products. For example, the energy loss in tires, which are rubber products, is closely linked to fuel economy and grip performance. Widely used methods for evaluating the energy loss in polymer materials are to evaluate the loss tangent (tan δ) which can be determined by dynamic viscoelasticity analysis (see Patent Literature 1).
However, the methods for evaluating the energy loss based on the loss tangent give large errors, failing to provide satisfactory measurement accuracy. Another problem is that, in cases where the difference in value between samples is small, the difference cannot be evaluated with good reproducibility.